A stochastic approach for the simulation of particle resuspension from rough substrates: Model and numerical implementation

•Development of a stochastic model for the simulation of particle resuspension.•Effect of fluctuating adhesion forces for particle rolling on rough surfaces.•Effect of fluctuating drag forces on the dynamics of resuspended particles.•Accurate results obtained when both fluctuations are properly captured by the model.

This paper presents a Lagrangian stochastic model to simulate colloid resuspension from rough surfaces. For that purpose, the extension of a recent proposition is discussed as well as the details of its numerical implementation. The basis of this model is a dynamical approach which reproduces explicitly the different steps involved in a three-stage scenario of particle resuspension where particles are set in motion (first stage); roll/slide along a rough surface due to varying force moments (second stage); and can be detached when a large-scale asperity is hit (third stage). The model treats separately hydrodynamic forces (drag force), adhesion forces (mainly due to interface chemical effects) and surface roughness through a two-level description (small-scale asperities and large-scale asperities) within a unified approach that combines the effects of fluid mechanics, interface chemistry and material properties. A description of the key points of the model brings forward the important role played by the number of small-scale asperities in contact with each particle; the pivot point around which particles can roll; the streamwise kinetic energy acquired as particles roll/slide along the surface; the probability to hit a large-scale asperity and the prediction of the actual detachment. Specific methods to simulate the trajectories of these stochastic processes are detailed and validated in a step-by-step manner with a specific emphasis put on the interplay between adhesion forces and particle dynamics. Finally, once each step has been separately assessed, the complete model is evaluated by comparing predictions to a realistic resuspension test-case for airborne colloids, showing that good and consistent numerical predictions are obtained with reasonable time steps.

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